Periodic Task Schedule Behaviors - celery.task.schedules

class celery.task.schedules.crontab(minute='*', hour='*', day_of_week='*', nowfun=<built-in method now of type object at 0x1026dd080>)

A crontab can be used as the run_every value of a PeriodicTask to add cron-like scheduling.

Like a cron job, you can specify units of time of when you would like the task to execute. It is a reasonably complete implementation of cron’s features, so it should provide a fair degree of scheduling needs.

You can specify a minute, an hour, and/or a day of the week in any of the following formats:

minute

• A (list of) integers from 0-59 that represent the minutes of an hour of when execution should occur; or
• A string representing a crontab pattern. This may get pretty advanced, like minute=”*/15” (for every quarter) or minute=”1,13,30-45,50-59/2”.

hour

• A (list of) integers from 0-23 that represent the hours of a day of when execution should occur; or
• A string representing a crontab pattern. This may get pretty advanced, like hour=”*/3” (for every three hours) or hour=”0,8-17/2” (at midnight, and every two hours during office hours).

day_of_week

• A (list of) integers from 0-6, where Sunday = 0 and Saturday = 6, that represent the days of a week that execution should occur.
• A string representing a crontab pattern. This may get pretty advanced, like day_of_week=”mon-fri” (for weekdays only). (Beware that day_of_week=”*/2” does not literally mean “every two days”, but “every day that is divisible by two”!)

is_due(last_run_at)

remaining_estimate(last_run_at)

class celery.task.schedules.crontab_parser(max_=60)

Parser for crontab expressions. Any expression of the form ‘groups’ (see BNF grammar below) is accepted and expanded to a set of numbers. These numbers represent the units of time that the crontab needs to run on:

digit   :: '0'..'9'
dow     :: 'a'..'z'
number  :: digit+ | dow+
steps   :: number
range   :: number ( '-' number ) ?
numspec :: '*' | range
expr    :: numspec ( '/' steps ) ?
groups  :: expr ( ',' expr ) *

The parser is a general purpose one, useful for parsing hours, minutes and day_of_week expressions. Example usage:

minutes = crontab_parser(60).parse("*/15")  # yields [0,15,30,45]
hours = crontab_parser(24).parse("*/4")     # yields [0,4,8,12,16,20]
day_of_week = crontab_parser(7).parse("*")  # yields [0,1,2,3,4,5,6]

parse(cronspec)

class celery.task.schedules.schedule(run_every=None, relative=False)

is_due(last_run_at)

Returns tuple of two items (is_due, next_time_to_run), where next time to run is in seconds.

See celery.task.base.PeriodicTask.is_due() for more information.

remaining_estimate(last_run_at)

Returns when the periodic task should run next as a timedelta.